In Praise of the Little Muscles

The more I learn about how animal bodies achieve motion, the more impressed I am by the mechanical engineering that has been achieved by Mother Nature through some millions of years of evolution. Prosthetic limbs and robot arms that have been built to date by humans can’t come close to duplicating Nature’s exquisite designs. For example, I recently saw the latest personal robotics research coming out of Willow Garage. They’re doing interesting work, though as someone who has watched robotics research from the sidelines for 30 years or so, it’s clear that real progress is still slow, and we’re still a long way from giving Nature any serious competition, either from a physical performance point of view or from a computational intelligence point of view.

As someone who has never really studied anatomy in any detail, I also never fully appreciated just how many muscles are engaged in simple motions, what it takes to use and control them properly, and just how important some of those little muscles that we tend to ignore can be. There’s nothing like an injury to a minor muscle to teach you what their importance and function are.

My first experience with a “minor” muscle injury was some years ago. I tore my right piriformis muscle doing a lunge while fencing. (Look up all the muscles mentioned here at Get Body Smart.)

The Piriformis is a little muscle under the Gluteus Maximus that is used for leg rotation at the hip. I knew I’d done something bad at the time, but I didn’t have much in the way of acute pain and mostly just ignored the injury. Some months later I was experiencing chronic but vague hip discomfort and a sense of looseness in the joint. A good physical therapist was able to diagnose the problem from my assortment of vague symptoms, and having diagnosed the problem (the muscle at that point was seriously knotted), it was a straightforward, if slow, process to undo the damage and get the muscle back to normal function.

Apparently, there aren’t a lot of nerves in these small muscles compared to the major skeletal power muscles, and one can’t necessarily feel the damage unless you find the muscle and start to really knead it—something that can be hard to do for a muscle that is hidden behind something much bigger. It took a year or so of regular rubbing (the corner of a countertop or table
worked great!) before the muscle stopped acting up from time to time.

I had a similar experience with the upper part of my right Soleus muscle. In that case the injured muscle was hidden underneath the big calf muscle (the Gastrocnemius). The Soleus contributes to flexing the foot, and thus is commonly stressed by running.

Again, I was experiencing vague calf pain while not having any obvious pain in the big muscles. Once identified, Soleus muscle damage can be easily massaged by lying on one’s back and resting the lower leg on the opposite bent knee. Move the lower leg back and forth over the knee with the Gastrocnemius fully relaxed, and you should easily be able to find any tender or knotted
areas. Even though I don’t have any particular damage problems with this muscle now, I still find it a useful post-run massage to do—the Soleus muscles often take a beating on a long hard run. Also, while I generally subscribe to the theory that warming up slowly is far more important than stretching (which can be downright counter productive, promoting rather than preventing injury), I do find it useful to stretch the Soleus muscles by flexing the foot up with the leg straight (which also stretches the Achilles tendon and attached structures).

My most recent experience was the most dramatic yet. It introduced me to yet another lesser-known muscle that I had been completely unaware of and left me unable to run for several weeks! After running many hundreds of trail miles over rough terrain with little more than routine sore muscles and the occasional minor bumps and scrapes, I managed to injure myself on the track! I was well warmed up and had just run a 7-minute mile (about as fast as I can go for that distance). After a lap or two of cooling down, I decided to sprint for 100 m or so. Mistake! I almost never really sprint, and I don’t really have well-developed sprinting muscles and technique. Again, I knew I’d hurt something, but I wasn’t quite sure what. A couple of days later, about seven miles into a twelve-mile trail run, I landed slightly wrong on the injured leg going downhill, and felt a sharp pain in my knee. After the acute pain subsided, I was suddenly unable to run at all, though I could still walk with minimal limping and was able to walk the rest of the way.

It turns out that the damaged muscle this time was the Popliteus. (And no, there was not any ligament or cartilage damage at this point.) This seeming unimportant muscle is located immediately behind the knee running diagonally across the leg from the outside (at the top) underneath the top of the Grastocnemius muscle. It’s pretty hard to find even when acutely injured, but it can be massaged (carefully! there are other sensitive structures nearby) if the Gastrocnemius is fully relaxed. The Popliteus muscle serves at least three important functions. First, though it has very little power being very small, it is the first muscle that fires when you bend your knee from a fully-extended position. Second, it helps hold the knee joint together. Third, it helps prevent you from “hyperextending” your knee (going past the normal maximum extension—straight leg). Lacking a normally functioning Popliteus muscle is surprising debilitating! The knee joint just doesn’t work right. Most joint motions involve multiple muscles that are fired in an exquisitely timed sequence to achieve the full action. The Popliteus fires first
for knee bending, and without it, your timing falls apart. The joint looseness and potential for hyperextension leave the joint cartilage vulnerable. My attempts to continue at least light running caused acute pain to develop at the medial meniscus, the main piece of cartilage padding the knee joint on the inside. The weak Popliteus muscle allowed excessive pinching of the
cartilage, especially on impact. In effect, the Popliteus muscle also plays a key role in the sequence of muscle firing that provides shock absorption as you land on your foot when running. This particular problem is peculiar to running; walking and bicycling were possible with little or no pain. (With most knee injuries, bicycling is painful, since it tends to put significant stress on the knee.) Of course, as with any injury, any limping or other change of gait, whether conscious or not, tends to stress other muscles that are compensating for the injured muscle in unusual ways. In this case, I got quite sore in the adductors in the opposite leg!

The good news is that, while recovery has been slow and I was unable to run much at all for a few weeks, no lasting damage occurred. I walked and bicycled more, and eased back into running with shorter, slower distances, being particularly cautious on the downhills. Ibuprofen and a simple knee brace also helped enable a little more activity sooner, and I managed not to lose too much conditioning. I also followed the recommendation to take a Glucosamine/Chondroitin supplement.

I also took advantage of the slower shorter distances to start to switch over to more “toe” running (landing on the ball of the foot rather than the heel). This reduced the impact on the medial meniscus, again allowing me to run more sooner, though it has required developing a slightly different set of running muscles. (You use parts of your Gastrocnemius muscles more for shock absorption when landing on the ball of your foot than you do when landing on your heel.) I’ve been experimenting with Vibram Five-Finger shoes, which I like a lot for running, and since these shoes have no padding whatsoever, landing on your heels
is not such a good idea, at least on rough surfaces, so I was already motivated to change my running style. But I’ll postpone a detailed report on these unusual shoes for another post.

Final notes: (1) If you’re wondering whether the new shoes caused or exacerbated the injury (I was wearing them when it happened), I can’t prove definitively that they didn’t, but I’m pretty convinced that there’s no connection. I’ve tried various shoes since and keep coming back the the Five Fingers as the shoes that cause the least stress post-injury, which is certainly suggestive that they couldn't have caused the injury in the first place. (2) I now know how to go about diagnosing problems like those described above without consulting medical professionals. There are, of course, a lot of good resources on the web that can help you sort through any specific problem. I started out this time with a Google search on “knee pain” and found a number of good diagnostic aids including a paper by Calmbach and Hutchins oriented at Family Physicians that helped me sort through what was plausible and what was not, and I am convinced that I have correctly described the injury. Of course, I have to add the usual sort of disclaimer that you shouldn’t “try this at home” and should always seek competent medical advice when needed. I just happen to have a certain tendency to do things myself anyway, and I’ve come to believe that, in many cases, I can do as well or better than any professionals I might try to hire to help me.

David